With reference to FIG. 1, a conventional stack-type IC module structure has a plurality of pads (311) disposed on the upper and the lower surfaces of a substrate (31) (or called chip carrier), conducting through the upper and lower surfaces, and soldered and electrically connected with a plurality of joints (312) such that the IC module structure (3) can be longitudinally stacked and electrically conducted. Generally, those joints (312) can be selected from one of a solder ball, a bump, a metal column, and a lead as disclosed in Taiwan Patent No. 1240394 ‘Semiconductor package structure adapted to 3D package’ and Taiwan Patent No. 1245385 ‘Stackable ball grid array package structure of multi-chip module’. However, the count of the longitudinal stack varies with the function expansion, and the thickness of the overall stacked structure is inconsistent, making that the structure fails to be applied to light, thin, short and tiny electronic products, e.g. micro memory device. Besides, in the past the longitudinally stacked IC modules are electrically conducted by using the joints (312) to bond with the pads (311). Therefore, the step requiring the connection through the joints (312) in production process inevitably make the reduction of assembly processes and production cost-down impossible. Moreover, when the longitudinally stacked structure is subjected to a stress, the joints (312) are easily destructed due to shock. This further leads to interior signal connection quality among those IC modules. Above all, owing to the high temperature arising from chip operation, the conventional IC module structure (3) is prone to the issue of bad heat dissipation.